Most of wireless sensor networks (WSN) researchtopics consider how to save the energy of the sensor nodes. However, in some applications of WSN, such as in the monitoring of an earthquake or forest wildfire, transmitting emergency data packets to the sink node as soon as possible is much more important than saving power. In this paper, we propose a Priority-based Hybrid Protocol (PHP) WSN model to provide a feasible WSN architecture, which can save the energy of the sensor nodes in normal situation, but will transmit emergency data packets in an efficient manner to the sink node. The simulation analysis shows that PHP obtains superior performance during emergency condition.

In a large-scale wireless sensor network, a topology is needed to gather state-based data from sensor network and efficiently aggregate the data given the requirements of balanced load, minimal energy consumption, and prolonged network lifetime. In this study, we proposed a ring-based hierarchical clustering scheme (RHC) consisting of four phases: predeployment, parent-child relationship building, deployment, and member join phases. Two node types are distributed throughout the network: cluster head nodes (type 1 node) and general sensor nodes (type 2 node). The type 1 node has better battery life, software capability, and hardware features than the type 2 node; therefore, the type 1 node is a better cluster head than type 2 node. Due to our IP naming rules and type 1 nodes as cluster heads, public key cryptography, such as RSA (Rivest, Shamir, Adleman), or ECC (Elliptic Curve Cryptosystem), is easily implanted to our system to strengthen our security. The sink node is the only certification authority in our system, but n level cluster heads can be extended to n level certification authorities if needed, where n is maximum number of level.

The transport message security provided by vehicles in VANETs is quite important; vehicle message should be real-time and it will be not complicated to validate message calculation. The method proposed in the essay is mainly to validate the identity by means of Bilinear Diffie-Hellman method, and make vehicles validate the authenticity of RSU and TA’s identity and the effectiveness of key. RSU and TA only need to validate vehicle identity, without helping vehicles produce any key. When vehicle identity validation is completed, vehicles will produce public value and transmit it to other RSU and vehicles, while other vehicles could validate the identity through the message from the sender and public value from RSU. The advantages of the method proposed in this essay are listed as follows. (1) Vehicles, RSU, and TA can validate mutual identities and the effectiveness of keys. (2) Vehicles can produce public value functions automatically, thus reducing key control risks. (3) Vehicles do not need to show certificates to validate their identities, preventing the certificates from attacking because of long-term exposure. (4) Vehicles adopt a pseudonym ID challenge to validate their own identities during the process of handoff. (5) Vehicle messages can be validated using the Bilinear Diffie-Hellman (BDH) method without waiting for the RSU to validate messages, thus improving the instantaneity of messaging. The method proposed in the essay can satisfy source authentication, message integrity, nonrepudiation, privacy, and conditional untraceability requirements.

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